Conference calls between more than two users can be conducted “online”—that is, over a suitable network, such as the Internet, possibly via a conference server—for instance in a virtual meeting or group calling scenario. A suitable user device (e.g. Personal Computer, Tablet Device, Smartphone, VoIP telephone etc.) participates in such a call using one or more loudspeakers and one or more microphones housed in, our coupled to, the user device. Typically, a user device joining a call may, at some stage, play-out an audible “ringtone” as part of this process.
In an online conference call scenario, a situation may arise in which two or more participants are in the same room or otherwise collocated (that is, in the vicinity of one another) during the conference call. For instance, a first user at a first user device may be participating in the call when a second user at a second user device in the same room joins the call. Any ringtone played-out by the second user device may be captured by the first user device and recognized in the microphone signal path of the first user device; if so, the first user may be notified of the possibility that another user in their vicinity has joined the call. The first user can then turn to the second user and if so ask him to mute his user device.